content: /* Copyright (C) 2016-2018 Alibaba Group Holding Limited
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  ==============================================================================*/
  
  // Protocol Buffers - Google's data interchange format
  // Copyright 2013 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf.nano;
  
  import java.io.IOException;
  
  /**
   * Reads and decodes protocol message fields.
   *
   * This class contains two kinds of methods:  methods that read specific
   * protocol message constructs and field types (e.g. {@link #readTag()} and
   * {@link #readInt32()}) and methods that read low-level values (e.g.
   * {@link #readRawVarint32()} and {@link #readRawBytes}).  If you are reading
   * encoded protocol messages, you should use the former methods, but if you are
   * reading some other format of your own design, use the latter.
   *
   * @author kenton@google.com Kenton Varda
   */
  public final class CodedInputByteBufferNano {
    /**
     * Create a new CodedInputStream wrapping the given byte array.
     */
    public static CodedInputByteBufferNano newInstance(final byte[] buf) {
      return newInstance(buf, 0, buf.length);
    }
  
    /**
     * Create a new CodedInputStream wrapping the given byte array slice.
     */
    public static CodedInputByteBufferNano newInstance(final byte[] buf, final int off,
                                               final int len) {
      return new CodedInputByteBufferNano(buf, off, len);
    }
  
    // -----------------------------------------------------------------
  
    /**
     * Attempt to read a field tag, returning zero if we have reached EOF.
     * Protocol message parsers use this to read tags, since a protocol message
     * may legally end wherever a tag occurs, and zero is not a valid tag number.
     */
    public int readTag() throws IOException {
      if (isAtEnd()) {
        lastTag = 0;
        return 0;
      }
  
      lastTag = readRawVarint32();
      if (lastTag == 0) {
        // If we actually read zero, that's not a valid tag.
        throw InvalidProtocolBufferNanoException.invalidTag();
      }
      return lastTag;
    }
  
    /**
     * Verifies that the last call to readTag() returned the given tag value.
     * This is used to verify that a nested group ended with the correct
     * end tag.
     *
     * @throws InvalidProtocolBufferNanoException {@code value} does not match the
     *                                        last tag.
     */
    public void checkLastTagWas(final int value)
                                throws InvalidProtocolBufferNanoException {
      if (lastTag != value) {
        throw InvalidProtocolBufferNanoException.invalidEndTag();
      }
    }
  
    /**
     * Reads and discards a single field, given its tag value.
     *
     * @return {@code false} if the tag is an endgroup tag, in which case
     *         nothing is skipped.  Otherwise, returns {@code true}.
     */
    public boolean skipField(final int tag) throws IOException {
      switch (WireFormatNano.getTagWireType(tag)) {
        case WireFormatNano.WIRETYPE_VARINT:
          readInt32();
          return true;
        case WireFormatNano.WIRETYPE_FIXED64:
          readRawLittleEndian64();
          return true;
        case WireFormatNano.WIRETYPE_LENGTH_DELIMITED:
          skipRawBytes(readRawVarint32());
          return true;
        case WireFormatNano.WIRETYPE_START_GROUP:
          skipMessage();
          checkLastTagWas(
            WireFormatNano.makeTag(WireFormatNano.getTagFieldNumber(tag),
                               WireFormatNano.WIRETYPE_END_GROUP));
          return true;
        case WireFormatNano.WIRETYPE_END_GROUP:
          return false;
        case WireFormatNano.WIRETYPE_FIXED32:
          readRawLittleEndian32();
          return true;
        default:
          throw InvalidProtocolBufferNanoException.invalidWireType();
      }
    }
  
    /**
     * Reads and discards an entire message.  This will read either until EOF
     * or until an endgroup tag, whichever comes first.
     */
    public void skipMessage() throws IOException {
      while (true) {
        final int tag = readTag();
        if (tag == 0 || !skipField(tag)) {
          return;
        }
      }
    }
  
    // -----------------------------------------------------------------
  
    /** Read a {@code double} field value from the stream. */
    public double readDouble() throws IOException {
      return Double.longBitsToDouble(readRawLittleEndian64());
    }
  
    /** Read a {@code float} field value from the stream. */
    public float readFloat() throws IOException {
      return Float.intBitsToFloat(readRawLittleEndian32());
    }
  
    /** Read a {@code uint64} field value from the stream. */
    public long readUInt64() throws IOException {
      return readRawVarint64();
    }
  
    /** Read an {@code int64} field value from the stream. */
    public long readInt64() throws IOException {
      return readRawVarint64();
    }
  
    /** Read an {@code int32} field value from the stream. */
    public int readInt32() throws IOException {
      return readRawVarint32();
    }
  
    /** Read a {@code fixed64} field value from the stream. */
    public long readFixed64() throws IOException {
      return readRawLittleEndian64();
    }
  
    /** Read a {@code fixed32} field value from the stream. */
    public int readFixed32() throws IOException {
      return readRawLittleEndian32();
    }
  
    /** Read a {@code bool} field value from the stream. */
    public boolean readBool() throws IOException {
      return readRawVarint32() != 0;
    }
  
    /** Read a {@code string} field value from the stream. */
    public String readString() throws IOException {
      final int size = readRawVarint32();
      if (size <= (bufferSize - bufferPos) && size > 0) {
        // Fast path:  We already have the bytes in a contiguous buffer, so
        //   just copy directly from it.
        final String result = new String(buffer, bufferPos, size, InternalNano.UTF_8);
        bufferPos += size;
        return result;
      } else {
        // Slow path:  Build a byte array first then copy it.
        return new String(readRawBytes(size), InternalNano.UTF_8);
      }
    }
  
    /** Read a {@code group} field value from the stream. */
    public void readGroup(final MessageNano msg, final int fieldNumber)
        throws IOException {
      if (recursionDepth >= recursionLimit) {
        throw InvalidProtocolBufferNanoException.recursionLimitExceeded();
      }
      ++recursionDepth;
      msg.mergeFrom(this);
      checkLastTagWas(
        WireFormatNano.makeTag(fieldNumber, WireFormatNano.WIRETYPE_END_GROUP));
      --recursionDepth;
    }
  
    public void readMessage(final MessageNano msg)
        throws IOException {
      final int length = readRawVarint32();
      if (recursionDepth >= recursionLimit) {
        throw InvalidProtocolBufferNanoException.recursionLimitExceeded();
      }
      final int oldLimit = pushLimit(length);
      ++recursionDepth;
      msg.mergeFrom(this);
      checkLastTagWas(0);
      --recursionDepth;
      popLimit(oldLimit);
    }
  
    /** Read a {@code bytes} field value from the stream. */
    public byte[] readBytes() throws IOException {
      final int size = readRawVarint32();
      if (size <= (bufferSize - bufferPos) && size > 0) {
        // Fast path:  We already have the bytes in a contiguous buffer, so
        //   just copy directly from it.
        final byte[] result = new byte[size];
        System.arraycopy(buffer, bufferPos, result, 0, size);
        bufferPos += size;
        return result;
      } else if (size == 0) {
        return WireFormatNano.EMPTY_BYTES;
      } else {
        // Slow path:  Build a byte array first then copy it.
        return readRawBytes(size);
      }
    }
  
    /** Read a {@code uint32} field value from the stream. */
    public int readUInt32() throws IOException {
      return readRawVarint32();
    }
  
    /**
     * Read an enum field value from the stream.  Caller is responsible
     * for converting the numeric value to an actual enum.
     */
    public int readEnum() throws IOException {
      return readRawVarint32();
    }
  
    /** Read an {@code sfixed32} field value from the stream. */
    public int readSFixed32() throws IOException {
      return readRawLittleEndian32();
    }
  
    /** Read an {@code sfixed64} field value from the stream. */
    public long readSFixed64() throws IOException {
      return readRawLittleEndian64();
    }
  
    /** Read an {@code sint32} field value from the stream. */
    public int readSInt32() throws IOException {
      return decodeZigZag32(readRawVarint32());
    }
  
    /** Read an {@code sint64} field value from the stream. */
    public long readSInt64() throws IOException {
      return decodeZigZag64(readRawVarint64());
    }
  
    // =================================================================
  
    /**
     * Read a raw Varint from the stream.  If larger than 32 bits, discard the
     * upper bits.
     */
    public int readRawVarint32() throws IOException {
      byte tmp = readRawByte();
      if (tmp >= 0) {
        return tmp;
      }
      int result = tmp & 0x7f;
      if ((tmp = readRawByte()) >= 0) {
        result |= tmp << 7;
      } else {
        result |= (tmp & 0x7f) << 7;
        if ((tmp = readRawByte()) >= 0) {
          result |= tmp << 14;
        } else {
          result |= (tmp & 0x7f) << 14;
          if ((tmp = readRawByte()) >= 0) {
            result |= tmp << 21;
          } else {
            result |= (tmp & 0x7f) << 21;
            result |= (tmp = readRawByte()) << 28;
            if (tmp < 0) {
              // Discard upper 32 bits.
              for (int i = 0; i < 5; i++) {
                if (readRawByte() >= 0) {
                  return result;
                }
              }
              throw InvalidProtocolBufferNanoException.malformedVarint();
            }
          }
        }
      }
      return result;
    }
  
    /** Read a raw Varint from the stream. */
    public long readRawVarint64() throws IOException {
      int shift = 0;
      long result = 0;
      while (shift < 64) {
        final byte b = readRawByte();
        result |= (long)(b & 0x7F) << shift;
        if ((b & 0x80) == 0) {
          return result;
        }
        shift += 7;
      }
      throw InvalidProtocolBufferNanoException.malformedVarint();
    }
  
    /** Read a 32-bit little-endian integer from the stream. */
    public int readRawLittleEndian32() throws IOException {
      final byte b1 = readRawByte();
      final byte b2 = readRawByte();
      final byte b3 = readRawByte();
      final byte b4 = readRawByte();
      return ((b1 & 0xff)      ) |
             ((b2 & 0xff) <<  8) |
             ((b3 & 0xff) << 16) |
             ((b4 & 0xff) << 24);
    }
  
    /** Read a 64-bit little-endian integer from the stream. */
    public long readRawLittleEndian64() throws IOException {
      final byte b1 = readRawByte();
      final byte b2 = readRawByte();
      final byte b3 = readRawByte();
      final byte b4 = readRawByte();
      final byte b5 = readRawByte();
      final byte b6 = readRawByte();
      final byte b7 = readRawByte();
      final byte b8 = readRawByte();
      return (((long)b1 & 0xff)      ) |
             (((long)b2 & 0xff) <<  8) |
             (((long)b3 & 0xff) << 16) |
             (((long)b4 & 0xff) << 24) |
             (((long)b5 & 0xff) << 32) |
             (((long)b6 & 0xff) << 40) |
             (((long)b7 & 0xff) << 48) |
             (((long)b8 & 0xff) << 56);
    }
  
    /**
     * Decode a ZigZag-encoded 32-bit value.  ZigZag encodes signed integers
     * into values that can be efficiently encoded with varint.  (Otherwise,
     * negative values must be sign-extended to 64 bits to be varint encoded,
     * thus always taking 10 bytes on the wire.)
     *
     * @param n An unsigned 32-bit integer, stored in a signed int because
     *          Java has no explicit unsigned support.
     * @return A signed 32-bit integer.
     */
    public static int decodeZigZag32(final int n) {
      return (n >>> 1) ^ -(n & 1);
    }
  
    /**
     * Decode a ZigZag-encoded 64-bit value.  ZigZag encodes signed integers
     * into values that can be efficiently encoded with varint.  (Otherwise,
     * negative values must be sign-extended to 64 bits to be varint encoded,
     * thus always taking 10 bytes on the wire.)
     *
     * @param n An unsigned 64-bit integer, stored in a signed int because
     *          Java has no explicit unsigned support.
     * @return A signed 64-bit integer.
     */
    public static long decodeZigZag64(final long n) {
      return (n >>> 1) ^ -(n & 1);
    }
  
    // -----------------------------------------------------------------
  
    private final byte[] buffer;
    private int bufferStart;
    private int bufferSize;
    private int bufferSizeAfterLimit;
    private int bufferPos;
    private int lastTag;
  
    /** The absolute position of the end of the current message. */
    private int currentLimit = Integer.MAX_VALUE;
  
    /** See setRecursionLimit() */
    private int recursionDepth;
    private int recursionLimit = DEFAULT_RECURSION_LIMIT;
  
    /** See setSizeLimit() */
    private int sizeLimit = DEFAULT_SIZE_LIMIT;
  
    private static final int DEFAULT_RECURSION_LIMIT = 64;
    private static final int DEFAULT_SIZE_LIMIT = 64 << 20;  // 64MB
  
    private CodedInputByteBufferNano(final byte[] buffer, final int off, final int len) {
      this.buffer = buffer;
      bufferStart = off;
      bufferSize = off + len;
      bufferPos = off;
    }
  
    /**
     * Set the maximum message recursion depth.  In order to prevent malicious
     * messages from causing stack overflows, {@code CodedInputStream} limits
     * how deeply messages may be nested.  The default limit is 64.
     *
     * @return the old limit.
     */
    public int setRecursionLimit(final int limit) {
      if (limit < 0) {
        throw new IllegalArgumentException(
          "Recursion limit cannot be negative: " + limit);
      }
      final int oldLimit = recursionLimit;
      recursionLimit = limit;
      return oldLimit;
    }
  
    /**
     * Set the maximum message size.  In order to prevent malicious
     * messages from exhausting memory or causing integer overflows,
     * {@code CodedInputStream} limits how large a message may be.
     * The default limit is 64MB.  You should set this limit as small
     * as you can without harming your app's functionality.  Note that
     * size limits only apply when reading from an {@code InputStream}, not
     * when constructed around a raw byte array.
     * <p>
     * If you want to read several messages from a single CodedInputStream, you
     * could call {@link #resetSizeCounter()} after each one to avoid hitting the
     * size limit.
     *
     * @return the old limit.
     */
    public int setSizeLimit(final int limit) {
      if (limit < 0) {
        throw new IllegalArgumentException(
          "Size limit cannot be negative: " + limit);
      }
      final int oldLimit = sizeLimit;
      sizeLimit = limit;
      return oldLimit;
    }
  
    /**
     * Resets the current size counter to zero (see {@link #setSizeLimit(int)}).
     */
    public void resetSizeCounter() {
    }
  
    /**
     * Sets {@code currentLimit} to (current position) + {@code byteLimit}.  This
     * is called when descending into a length-delimited embedded message.
     *
     * @return the old limit.
     */
    public int pushLimit(int byteLimit) throws InvalidProtocolBufferNanoException {
      if (byteLimit < 0) {
        throw InvalidProtocolBufferNanoException.negativeSize();
      }
      byteLimit += bufferPos;
      final int oldLimit = currentLimit;
      if (byteLimit > oldLimit) {
        throw InvalidProtocolBufferNanoException.truncatedMessage();
      }
      currentLimit = byteLimit;
  
      recomputeBufferSizeAfterLimit();
  
      return oldLimit;
    }
  
    private void recomputeBufferSizeAfterLimit() {
      bufferSize += bufferSizeAfterLimit;
      final int bufferEnd = bufferSize;
      if (bufferEnd > currentLimit) {
        // Limit is in current buffer.
        bufferSizeAfterLimit = bufferEnd - currentLimit;
        bufferSize -= bufferSizeAfterLimit;
      } else {
        bufferSizeAfterLimit = 0;
      }
    }
  
    /**
     * Discards the current limit, returning to the previous limit.
     *
     * @param oldLimit The old limit, as returned by {@code pushLimit}.
     */
    public void popLimit(final int oldLimit) {
      currentLimit = oldLimit;
      recomputeBufferSizeAfterLimit();
    }
  
    /**
     * Returns the number of bytes to be read before the current limit.
     * If no limit is set, returns -1.
     */
    public int getBytesUntilLimit() {
      if (currentLimit == Integer.MAX_VALUE) {
        return -1;
      }
  
      final int currentAbsolutePosition = bufferPos;
      return currentLimit - currentAbsolutePosition;
    }
  
    /**
     * Returns true if the stream has reached the end of the input.  This is the
     * case if either the end of the underlying input source has been reached or
     * if the stream has reached a limit created using {@link #pushLimit(int)}.
     */
    public boolean isAtEnd() {
      return bufferPos == bufferSize;
    }
  
    /**
     * Get current position in buffer relative to beginning offset.
     */
    public int getPosition() {
      return bufferPos - bufferStart;
    }
  
    /**
     * Retrieves a subset of data in the buffer. The returned array is not backed by the original
     * buffer array.
     *
     * @param offset the position (relative to the buffer start position) to start at.
     * @param length the number of bytes to retrieve.
     */
    public byte[] getData(int offset, int length) {
      if (length == 0) {
        return WireFormatNano.EMPTY_BYTES;
      }
      byte[] copy = new byte[length];
      int start = bufferStart + offset;
      System.arraycopy(buffer, start, copy, 0, length);
      return copy;
    }
  
    /**
     * Rewind to previous position. Cannot go forward.
     */
    public void rewindToPosition(int position) {
      if (position > bufferPos - bufferStart) {
        throw new IllegalArgumentException(
                "Position " + position + " is beyond current " + (bufferPos - bufferStart));
      }
      if (position < 0) {
        throw new IllegalArgumentException("Bad position " + position);
      }
      bufferPos = bufferStart + position;
    }
  
    /**
     * Read one byte from the input.
     *
     * @throws InvalidProtocolBufferNanoException The end of the stream or the current
     *                                        limit was reached.
     */
    public byte readRawByte() throws IOException {
      if (bufferPos == bufferSize) {
        throw InvalidProtocolBufferNanoException.truncatedMessage();
      }
      return buffer[bufferPos++];
    }
  
    /**
     * Read a fixed size of bytes from the input.
     *
     * @throws InvalidProtocolBufferNanoException The end of the stream or the current
     *                                        limit was reached.
     */
    public byte[] readRawBytes(final int size) throws IOException {
      if (size < 0) {
        throw InvalidProtocolBufferNanoException.negativeSize();
      }
  
      if (bufferPos + size > currentLimit) {
        // Read to the end of the stream anyway.
        skipRawBytes(currentLimit - bufferPos);
        // Then fail.
        throw InvalidProtocolBufferNanoException.truncatedMessage();
      }
  
      if (size <= bufferSize - bufferPos) {
        // We have all the bytes we need already.
        final byte[] bytes = new byte[size];
        System.arraycopy(buffer, bufferPos, bytes, 0, size);
        bufferPos += size;
        return bytes;
      } else {
        throw InvalidProtocolBufferNanoException.truncatedMessage();
      }
    }
  
    /**
     * Reads and discards {@code size} bytes.
     *
     * @throws InvalidProtocolBufferNanoException The end of the stream or the current
     *                                        limit was reached.
     */
    public void skipRawBytes(final int size) throws IOException {
      if (size < 0) {
        throw InvalidProtocolBufferNanoException.negativeSize();
      }
  
      if (bufferPos + size > currentLimit) {
        // Read to the end of the stream anyway.
        skipRawBytes(currentLimit - bufferPos);
        // Then fail.
        throw InvalidProtocolBufferNanoException.truncatedMessage();
      }
  
      if (size <= bufferSize - bufferPos) {
        // We have all the bytes we need already.
        bufferPos += size;
      } else {
        throw InvalidProtocolBufferNanoException.truncatedMessage();
      }
    }
  
    // Read a primitive type.
    Object readPrimitiveField(int type) throws IOException {
      switch (type) {
        case InternalNano.TYPE_DOUBLE:
            return readDouble();
        case InternalNano.TYPE_FLOAT:
            return readFloat();
        case InternalNano.TYPE_INT64:
            return readInt64();
        case InternalNano.TYPE_UINT64:
            return readUInt64();
        case InternalNano.TYPE_INT32:
            return readInt32();
        case InternalNano.TYPE_FIXED64:
            return readFixed64();
        case InternalNano.TYPE_FIXED32:
            return readFixed32();
        case InternalNano.TYPE_BOOL:
            return readBool();
        case InternalNano.TYPE_STRING:
            return readString();
        case InternalNano.TYPE_BYTES:
            return readBytes();
        case InternalNano.TYPE_UINT32:
            return readUInt32();
        case InternalNano.TYPE_ENUM:
            return readEnum();
        case InternalNano.TYPE_SFIXED32:
            return readSFixed32();
        case InternalNano.TYPE_SFIXED64:
            return readSFixed64();
        case InternalNano.TYPE_SINT32:
            return readSInt32();
        case InternalNano.TYPE_SINT64:
            return readSInt64();
        default:
            throw new IllegalArgumentException("Unknown type " + type);
      }
    }
  }
  